SainSmart MQ8 DC 3-5V 10-1000ppm Carbonic Oxide Gas Sensor Module Detector for Arduino Analog 0 ~ 5 v voltage, the higher the concentration, the higher the voltage. High sensitivity to hydrogen. Can be resistant to ethanol steam, LPG (petroleum), smoke interference Has a long service life and reliable stability. Quick response recovery features Dual signal output (TTL level output and analog output). TTL output valid signal for low level.